I would look at the Aberlour A'bunadh (The Origin). Great whisky. Probably not what he's sipping on if he's buying 'cheap' bottles, although it really isn't much more $$ than their 10yr or 12yr. It'll taste familiar to him, yet it'll be a step up. Just make sure that's not what he's already drinking, lol.
Beyond that, I would look at maybe a Macallan Cask Strength (perhaps because that's what I'm savouring at this very moment) It's 59.3% Sherried (which most ppl think is a good thing). A good Scotch at a reasonable price again.
If you wish to push the upper echelons of your budget you set out, I would gift a bottle of Glenmorangie Signet. To describe the nose and taste... Take a whole dark choclate bar and dissolve it in a bottle of great whisky, and there you go. You wanna stand out on your Dad's bday, then this is the bottle I'd go with (in this price range, but it's a great scotch at any price).
My $0.02cdn. Good luck